How to index and search business objects with Lucene.Net?
I would like to know how to use Lucene.NET to index and search my business objects. I see NHibernate.Search has nice features for this problem, but it still needs a DB. I don't need a DB, I want to store all data in my Lucene.NET index. I can also see that a java framework like Compass can do this easily, but it is not a .NET library.
Is there a way to create or design objects to solve this problem?
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try this code to use Lucene.NET to index business entity snapshots .. this has obvious property type constraints and requires error checking but gives you a general idea of how to achieve this.
public class IndexHelper
{
static Analyzer analyzer = new StandardAnalyzer();
// Store the index in memory:
static Directory directory = new RAMDirectory();
static IndexWriter iwriter;
static Dictionary<string, List<WeakReference>> indexedObjects = new Dictionary<string, List<WeakReference>>();
static IndexHelper()
{
iwriter = new IndexWriter(directory, analyzer, true);
iwriter.SetMaxFieldLength(25000);
}
public static void IndexObject(object entity)
{
Document doc = new Document();
PropertyInfo[] entityProperties = entity.GetType().GetProperties();
string entityKey = entity.GetHashCode().ToString();
List<WeakReference> entityList;
if (indexedObjects.TryGetValue(entityKey, out entityList) == false)
{
entityList = new List<WeakReference>();
indexedObjects.Add(entityKey, entityList);
}
entityList.Add(new WeakReference(entity));
doc.Add(new Field("@HASH", entityKey, Field.Store.YES, Field.Index.UN_TOKENIZED));
foreach (PropertyInfo pInfo in entityProperties)
{
String propertyName = pInfo.Name;
object propertyValue = pInfo.GetValue(entity, null); //Assuming all properties are of non index type
String text = "null";
if (propertyValue != null) text = propertyValue.ToString();
doc.Add(new Field(propertyName, text, Field.Store.YES,
Field.Index.TOKENIZED));
}
iwriter.AddDocument(doc);
iwriter.Close();
}
public static List<WeakReference> Search(string queryString, string fieldName)
{
// Now search the index:
IndexSearcher isearcher = new IndexSearcher(directory);
Lucene.Net.QueryParsers.QueryParser qp = new Lucene.Net.QueryParsers.QueryParser(fieldName, analyzer);
qp.SetDefaultOperator(Lucene.Net.QueryParsers.QueryParser.OR_OPERATOR);
qp.SetLowercaseExpandedTerms(true);
Query query = qp.Parse(queryString);
List<WeakReference> results = new List<WeakReference>();
Hits hits = isearcher.Search(query);
// Iterate through the results:
for (int i = 0; i < hits.Length(); i++)
{
Document hitDoc = hits.Doc(i);
List<WeakReference> matchedObjects;
if (indexedObjects.TryGetValue(hitDoc.GetField("@HASH").StringValue(), out matchedObjects))
{
results.AddRange(matchedObjects);
}
}
isearcher.Close();
return results;
}
}
Update: also have a look at this project http://www.codeplex.com/linqtolucene
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